1. Field of the Invention
This invention relates to a light charging type secondary battery unit in which a photo-electric transducer and a storage battery are unified together. This invention also relates to an electrical equipment having both a photo-electric transducer and a storage battery unit.
2. Description of the Related Art
The photo-electric transducer, also termed a solar cell, is a device for converting light energy, such as that from the sunbeams, into an electrical energy. In distinction from a fossil fuel, utilized up to now, the photo-electric transducer scarcely emits an exhaust gas, such as carbon dioxide, when recovering the electric energy from the light energy. Also, since the photo-electric transducer recovers the electric energy from the light energy of a sunbeam, which is felt to be limitless, power generation can be assured semi-permanently. For this reason, the photo-electric transducer presumably finds an increasing field and scope of application in view of the incumbent problem of the global environment.
However, the photo-electric transducer frequently undergoes temporal fluctuations in the amount of the light energy from the sunbeams, such that the electric energy recovered by conversion from the light energy also undergoes temporal fluctuations, with the result that the photo-electric transducer can frequently not be usable as a direct power source for electric equipments.
Also, since the light energy such as that from the sunbeams is present in a spatially rarefied state, the photo-electric transducer is in need of a large light reception area in order to acquire the power of a pre-set quantity suitable for utilization.
Thus, the photo-electric transducer is used as an auxiliary power source for electric equipment or in a field in which the generated electric energy is transiently stored in a storage battery and used as the power discharged from the storage battery.
On the other hand, electrical equipment is progressively reduced in size with the recent progress in various processing techniques and frequently used as portable equipment. For this reason, the usual power source for the electrical equipment is a dry cell which is convenient for its portability, and hence there is possibility of an increasing demand for dry cells in the future.
However, the dry cell is usually a primary cell, such as a manganese dry cell or an alkali manganese dry cell, and is discarded after discharging its stored energy. Thus, dry cells cannot be said to be desirable because of economic considerations, wastage of natural resources and load imposed on the environment. Although a secondary battery having the standard shape similar to that of the dry cell, such as a NiMH cell, is in use, it cannot be said to be optimum, as the primary battery, if the battery is charged by means which possibly imposes loads on the global environment.
There has also been proposed in, for example, Japanese Laid-Open Patent S-63-314780 entitled "Battery" or in Japanese Laid-Open Patent H-2-73675 entitled "Cylindrically-Shaped Charging Type Solar Cell", a light charging type secondary battery unit which combines the above-described merit of the photo-electric transducer and the ease in handling proper to the dry cell. The conventional light charging type secondary battery unit, combining the photo-electric transducer as a power generating portion and the storage battery as a charging/discharging portion, realizes the driving of an ordinarily used electrical equipment by the power generated by the light energy.
However, with the conventional light charging type secondary battery unit since the photo-electric transducer receives the light energy of sunbeams, which illuminate from a pre-set direction, it is difficult to utilize the totality for the outer surface of the storage battery. Moreover, it is not possible with the conventional light charging type secondary battery unit to have a light receiving area of the photo-electric transducer which is in excess of the outer surface of the storage battery. Therefore, the conventional light charging type secondary battery unit has a drawback that the battery charging time is unbearably long, while the photo-electric transducer cannot develop the power required for charging the storage cell.